Acrylamidic graft copolymers and their preparation



United States Patent C) 3,026,293 ACRYLAMIDIC GRAFT COPOLYMERS AND THEIR PREPARATION John R. Caldwell and Harry W. Coover, Jr., Kingsport,

Tenn., assignors to Eastman Kodak Compauy,'Rochester, N.Y., a corporation of New Jersey No Drawing. Continuation of application Ser. No. 444,648, July 20, 1954. This application Aug. 6, 1959, Ser. No. 831,942

6 Claims. (Cl. 260-455) This invention relates to graft copolymers of the type wherein one or more monomeric materials are polymerized in admixture with a preformed homopolymer or interpolymer, and is particularly concerned with the preparation of acrylamidic graft copolymers wherein a major portion of the preformed polymer is an acrylamidic monomer in polymerized form.

A large number of polymeric materials have been prepared in the past, including homopolymers, interpolymers, and more recently graft copolymers. The homopolymers are prepared by polymerizing a single polymerizable monomer containing at least one CH=C group. Usually the homopolymers are polymers obtained by polymerizing a vinylic monomer which is an olefinic material containin a single ethylenic group of this kind. The interpolyrners include copolymers which are prepared by simultaneously copolymerizing a mixture of olefinic monomers which can be either two vinylic monomers, or a vinylic monomer and a diolefinic monomer, or two diolefinic monomers. Terpolymers are prepared by simultaneously polymerizing an admixture of three such polymerizable olefinic monomers. Graft copolymers are prepared by polymerizing one or more olefinic monomers in admixture with a preformed homopolymer or interpolymer, whereby a directed structural configuration in the polymer molecule is obtained in contrast to the random distribution obtained in interpolymers by simultaneous polymerization of two or more monomers. In graft copolymerization, a single olefinic monomer can be polymerized with the preformed polymer, or a mixture of olefinic monomers, including either or both vinylic and diolefim'c monomers, can be polymerized with the preformed polymer. The graft copolymerization can take place with the preformed polymer directly in the polymerization reaction mixture in which the preformed polymer is formed and from which it has not been isolated, in which case the preformed polymer is designated as a live polymer. Alternatively, the preformed polymer can be isolated from its polymerization mixture, and such isolated polymers are designated as dead polymers. The graft copolymers appear to have an integral polymer structure since, unlike mixtures of polymers, the components cannot be separated by solvent partition or other means ordinarily employed for separating mixtures of polymers. As a consequence, the graft copolymers possess properties quite unlike mixtures of polymers, and also quite unlike the properties of interpolymers prepared by simultaneous polymerization of the various monomers entering into the polymeric compounds.

One of the primary advantages of the synthetic polymeric materials over naturally occurring materials is the fact that the chemical constitution and structural configuration can be controlled to a certain extent to give the desired properties to the resulting polymers. Usually, however, the properties cannot be predicted accurately in advance, and hence the preparation of polymeric materials is largely an empirical science. Prior to this invention, attempts have been made to prepare polymeric materials which would have the property of transmitting water vapor freely without at the same time allowing the passage of liquid water. The utility of such a material is obvious, since such a material would an 1 C furnish waterproof films which could breathe in a manner analogous to the usual textile fabrics. Most polymeric film-forming materials which exhibit water resistance are highly impervious to water vapor also and hence have limited utility in the preparation of wearing apparel because of discomfort. Another property of such materials which is desirable is that they be flexible and retain their flexibility even after prolonged exposure to liquid water. Attempts have been made to polymerize polyvinyl alcohol films to give flexibility and to cross-link the films to give water insolubility. Such films will transmit water vapor, but the plasticizer is usually leached from the film by contact with liquid water or aqueous solutions, and a brittle, inflexible product is obtained when the film is dried.

In addition to polymeric materials which will transmit water vapor while retaining liquid water, it is desirable to prepare polymeric films which have the ability of absorbing water whereby the film is swelled without being completely washed away. Such polymers would find particular utility in the photographic arts where they would function in much the same manner as does gelatin, as well as in the textile and paper sizing arts.

It is accordingly an object of this invention to provide new and improved polymeric materials which have unusual solubility and vapor transmission characteristics and which are capable of remaining flexible even after prolonged exposure to liquid water or aqueous solutions.

It is a further object of the invention to prepare improved polymers which freely transmit water vapor without permitting the passage of liquid water, and which form strong, flexible films having excellent abrasion resistance and wearing qualities.

Another object of the invention is to provide a new type of graft copolymers involving an acrylarnidic preformed polymer graft polymerized with certain monomeric materials as defined herein in particular ranges of proportions of the various components whereby highly unusual and highly useful properties are obtained which could not be satisfactorily obtained with the polymers known to the art prior to this invention.

Another object of this invention is to provide improved polymeric materials which offer unusual advantages in the textile coating, the paper sizing, flexible film and photographic arts.

Other objects will be apparent from the description and claims which follow.

These and other objects are attained by means of this invention, which comprises providing polymeric material having the desirable properties described hereinabove by graft copolymerizing a mixture of (1) 2080% by weight of preformed polymeric material composed of combined monomeric material which consists of (a) 70l00% by weight of at least one acrylamidic monomer of the formula are free of multiple linkages other than olefinic linkages of this type or carbonylic linkages of the type The polymeric materials which correspond in chemical constitution and structural configuration to the graft V copolyrners thus obtained possess unusual and highly advantageous properties. The polymers which contain from 'to 60% of the preformed polymeric material (containing 70-100% by weight of combined acrylamidic monomer) are especially valuable in the preparation of films which freely transmit water vapors but which do not pernnt the passage of liquid water. Polymers of the invention containing higheramounts of preformed polymers up to 80% by weight ofthe entire graft polymer have the property of being swelled by water or'aqueous solutions and hence are excellent water-dispersible colloids which are very useful as gelatin substitutes, extenders or additives, or as thickening agents or sizing agents. The polymers of the invention can be readily prepared directly in the form of a smooth emulsion which can be employed for coating or film casting applications, or they can *be prepared in dried form suitable for molding or shaping into any of the shaped objects commonly prepared from polymeric materials. The dried polymers are also capable of being dissolved in a suitable organic solvent to form dopes or of being redisper'sed into aqueous emulsions. The polymers can also be treated with a hardening or cross-linking agent for the acrylamidic polymer whereby the'water insolubility is increased as well as being graft polymerized in the presence of the divinyl cross-linking agent for the portion of the polyrner polymerized during the grafting step whereby insolubih'ty in the common organic solvents is obtained. It is thus apparent that the polymeric materials of this invention can be used for a wide variety of applications, and that the solubility characteristics as regards both water and organic solvents, as well as the water vapor transmitting characteristics, Can be varied over a wide range in accordance with the desired properties in the product.

Particularly useful polymeric materials result from graft copolymerizing a mixture of (1) 20-80% by weight of preformed polymers composed of combined monomeric material consisting of (a) 70-100% by weight of one or more acrylamidicmonomers as defined and (b) ISO-0% by Weight of one or more-vinylic monomers with (2) 80% 10% by weight of polymerizable olefinic monomer or monomers including 60l00% by weight of one or more alkyl acrylates resulting from esterifying acrylic acid with an aliphatic alcohol of 1-8 carbon atoms, or a diolefinic monomer containing the group In addition to the acrylate or diolefinic monomer or monomers, up to 40% by weight based on the total weight of the olefinic monomers employed in'the grafting step, of one or more other polymerizable vinylic monomers can be employed. The polymers wherein the acrylate monomer is employed in the grafting step are of particular utility in the formation of films wherein a high differential between the water vapor and liquid water transmission rates is desired. The polymers containing the diolefinicmonomer are-particularly advantageous because of their rubbery flexible properties and hence are desirably'em'ployed in applications wherein resistance to abrasion is of particular importance.

Inthe polymers of this invention, at'least 60% by weight-ofthe graftingmonomer-or'monomers (i.e. the monomers'employed for graft copolymerizing with the preformedpolymer), are unhalogenated, are not acrylamidic monomersas defined hereinabove, contain at least one olefinic or ethylenic unsaturation, and contain no multiple linkages other than olefinic and carbonylic linkages. it will be understood that the reference to carbonylic linkages does not infer the presence of a ketoor aldehydrooxygen but also refers to the carbonylic linkage of an amide, carboxylic acid or carboxylate ester. Halogenated monomers such as vinyl chloride and vinylidene chloride as well as monomers containing other multiple cyano linkages, such as acrylonitrile or similar vinyl compounds, can-be usedin amounts up .to 40% of the total weight of the grafting monomers. Similarly, the minor constituent of the grafting monomers, when a mixture of monomers is employed, can be an acrylamidic monomer such as an acrylamide -or a methacrylamide, and including the N-alkylated as well as the N,N-dialkylated acrylamides and methacrylamides.

Although the acrylate monomers and the diolefinic monomers possess particular utility in the preparation of the polymers of this invention, highly useful compositions can be prepared without employing either of these types of monomers or by using such monomers in minor amounts. Thus, for example, any desired'portion of the grafting monomers can be an ethylenically unsaturatedmonocarboxylic acid which is polymerizable or interpolymerizable, and including such acids as acrylic acid, meth acrylic acid, maleic acid, furnaric acid, itaconic acid,- citraconicacid, and similar unsaturated acids, as wellas the amides, allryl esters, amates, and similar polymerizeble derivatives of these and other polymerizable unsaturated carboxylicacids. The minor constituents which can be employed also include the vinyl esters of these and similar aliphatic carboxylic acids containing 2 to l 0 carbon atoms, vinyl ethers, vinyl ketones, vinyl pyridines, aryl compoundsisuch as the styrene and substituted styrenes, N-vinyl imides, N-vinyl lactams, as Well as polymerizable hydrocarbons such as ethylene, rsobutylene, and the like.

The preformed polymer used inpreparing the graft copolymers of the invention forms from 20 to 80% of the .total Weight of the graft copolymer, and from 70 to 100% of the weight of this ,preformed polymerconsists of one or more acrylamidic monomers, in the polymerized-form, of the formula I't R" 1 'I' wherein R 15 either hydrogen or a methyl group and R mers suitable for usein practicingthe invention are acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N -butyl acrylamide, -N,N -dimethyl acrylamide, 'N-isopropyl acrylamide, methacrylamide, N-methyl methacrylamide, N-propyl methacrylamide, N-isobutyl methacrylarnide, and'N,N-diethyl'methacrylamide, and similar derivatives of acrylamide and methacrylamitle. In practicing the invention, -a-single-acrylamidic monomer can be used or mixtures'of two or more acrylamidic monomers as'defined can be-usedin preparing the preformed polymer.

The preformed polymer can consist entirely of polymerized acrylamidic monomers or can contain up to 30% of theweight of preformed polymer of a different vinylic monomer containing a single ethylenic unsaturation. A large number of such vinylic monomers are specifically described herein, and it will be'understood that any one or more of the :vinylic-monomers containing a -CH=C group can be used.

The preformed polymer can be preparedin any well known manner as, for example, by dissolving or dispersing the monomer'or monomers to be employed in forming the polymer in water or in a suitable organic solvent and adding a polymerization catalyst to the dispersion. The polymerization can thereafter be effected at temperatures varying from room temperature to the refiux'temperature of the reaction mixture. Ordinarily, a temperature. of from 25 to '75 C. is sufficient. The preparation of the preformed polymer is-tuus carried outin accordance with usual practice. Any of the polymerization catalysts can be employed including the well known per'catalysts such as benzoyl peroxide, acetyl peroxide, lauryl peroxide, triacetone peroxide, urea peroxide, t-butyl hydroperoxide, hydrogen peroxide, alkali metal perborates such as sodium and potassium perborate, persulfates such as alkali metal or ammonium persulfates, alkyl percarbonates, as well as such catalysts as the ketazines, azines, and the like, and including materials such as azo-bis-isobutyro nitrile. The quantity of catalyst employed can be varied in accordance with usual polymerization practices depending upon the nature and ratio of reactants, the reaction conditions, and similar variable factors.

The polymerization can be carried out advantageously in aqueous medium, although aqueous solvents such as aqueous acetone or the like can be used with satisfactory results. The polymerization can be either in emulsion or in solution, and the term dispersion polymerization is intended to include either of these variations. The acrylamidic monomers are readily soluble in water, and the particular polymerization system will depend upon whether or not one or more other monomers are used and the nature of such monomers. Following the polymerization, the acrylamidic polymer thereby obtained can be isolated from the polymerization reaction mixture and used in the form of a dead preformed polymer in the subsequent grafting stage, or the preformed polymer can be left in the ploymerization reaction mixture and the grafting monomer added directly thereto, whereby polymerization is effected with a live preformed polymer. It will be understood, that any of the polymerization adjuncts commonly employed such as emulsifiers, chain length regulators, and similar polymerization aids can be employed in accordance with usual practice. In carrying out the polymerization, up to 30% by weight of the monomeric material employed in forming the preformed polymer can be one or more vinylic monomers such as the polymerizable unsaturated carboxylic acids, their amides, esters, amates, and the like, as well as the vinyl derivatives of benzene such as the styrene and substituted styrene monomers, the vinyl pyridines, including the alkyl substituted vinyl pyridines, the vinyl ethers, vinyl ketones, acrylonitrile monomers such as acrylonitrile itself or a substituted acrylonitrile such as methacrylonitrile, vinyl chloride, vinylidene chloride, or any of the other well known vinylic monomers.

In accordance with this invention, from 20 to 80 parts by weight of the preformed acrylamidic polymer is then graft copolymerized with from 80 to 20 parts by weight of grafting monomer or monomers. The polymerization during the grafting step is effected in accordance with well known polymerization practice as described in connection with the preparation of the preformed polymer. Thus the graft copolymerization can be carried out in an organic solvent using an isolated preformed polymer, or it can be carried out directly in the reaction mixture in which the preformed polymer was formed, regardless of whether such mixture is aqueous or organic in nature. It is preferred to carry out the graft copolymerization in aqueous media whereby a smooth emulsion is obtained which can be used directly for coating textiles, paper, leather, or the like, or used for depositing films of the polymer. In this regard, the preformed polymer is readily dispersed in water and hence an isolated polymer can be used in this manner. If desired, a promoter such as potassium sulfite or potassium bisulfite can be added to the polymerization mixture to increase the speed of reaction. The water soluble catalysts such as sodium persulfate, potassium persulfate, sodium perborate, hydrogen peroxide or similar per-catalysts are desirably employed in amounts of from 0.05% to 3.0%, and preferably from 0.5% to 1.0% based on the total weight of grafting monomers. The polymerization is desirably effected by agitating the polymerization mixture at a temperature of 30-120" 0, and preferably at 50-75 C. for a period 6 of 3 to 12 hours. The graft copolymerization, as well as the formation of preformed polymers, can be carried to completion or can be stopped before complete polymerization has been effected as desired.

The graft copolymerization is desirably carried out in aqueous solution wherein the concentration of preformed polymer is from 5 to 30%. Emulsifying agents such as the sodium salts of fatty alcohol sulfates, aromatic sulfonates, soaps and the like can be used but are not essential in most cases.

As has been described, particularly advantageous results are obtained when 60-100% of the grafting monomer consists of either one or more alkyl acrylates or one or more diolefins. As is described hereinbelow and shown in the examples of preferred embodiments, any of the other olefinic monomers and desirably the vinylic monomers can be used, with 60 to of the grafting monomer being unhalogenated and containing no multiple linkages other than olefinic or carbonylic linkages.

It is sometimes desirable to increase the resistance of the vinyl polymer to organic solvents, particularly when the polymer is to be employed in coating textiles, leather or the like. This can be readily accomplished by effecting the graft copolymerization in the presence of 1l5% by Weight of a cross-linking agent based on the total weight of grafting monomer. The cross-linking agent employed is desirably a divinyl material such as divinyl benzene, allyl acrylate, dallyl phthalate, or similar material containing two vinyl groups whereby cross-linking in the polymer results. Such dinvinyl cross-linking agents are well known in the art, and it is intended that this inventon shall include the use of any of such materials.

It is also desirable in many cases to harden the polymer to increase its water insolubility. This is true particularly when the polymer is to be employed in an application Where water vapor transmission is desired, without passage of liquid Water, and without objectionable swelling of the polymeric film. This hardening of the graft copolymer is readily accomplished by incorporating from 0.5% to 15.0% by weight based on the weight of the preformed polymer of a cross-linking agent or hardening agent for acrylamide polymers into the dispersion of graft copolymer before use. A large number of hardening or cross-linking agents for acrylamide polymers are known, and any of these materials can be employed. Suitable materials which are typical include formaldehyde, methylol ureas, methylol melamines, zirconium salts, polybasic acids, and the like. Best results are obtained with amounts of hardening agent of from 2% to 10% by weight based on the weight of the preformed polymer. The smooth, viscous emulsion or cream containing the graft copolymer and obtained as a product of the graft copolymerization can be used directly for coating, extruding, dipping, or the like. Evaporation of the emulsion leaves a clear, flexible, tough film. The emulsion can be coated on fabrics, leather, paper or other surfaces by the usual methods employing rolls or doctor blades. For the preparation of waterproof fabrics or leather from 0.6 to 6 oz. per square yard, and preferably from 1.5 to 3.0 oz. per square yard is used. The coated article can then be dried at l00-120 C. The dispersions can also contain any of the usually employed ingredients, including fire retarding agents such as tricresyl phosphate, triphenyl phosphate, chloroethyl phosphate, or the like, as well as pigments such as titanium dioxide, clay, carbon black, lead chromate, or the like.

en the preformed polymer is not readily soluble in water, it may be desirable to carry out the graft copolymerization in an organic solvent. For this purpose, the lower alcohols such as methyl, ethyl, propyl, or butyl alcohol, alcohol-ether mixtures, dioxane, or similar solvents or solvent mixtures can be used. In this case, the graft copolymer is obtained in the form of a dope or solution in the solvent, and this dope or solution can be used .for coating textiles, leather, and the like in the same manner .as the aqueous dispersions.

- The acrylate esters which are preferably employed in practicing the invention include any of the esters obtained by este'rifying acrylic acid .with an aliphatic alcohol of 110 8 carbon atoms. Thus,.for example, typical acrylic esters derived from either straight or branched-chain alcoholsinclude :rnethyl vacrylate, ethyl acrylate, propyl acrylate, -n-butyl .acrylate, see-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, cyclohexyl acrylate, Z-ethylhexyl acrylate, and the like. The acrylic esters of ether-alcohols are also useful, as, for example, the acrylic esters of the monoethyl ether of ethylene glycol, the acrylic ester of the monomethyl ether of ethylene. glycol, the acrylic ester of the monomethyl ether of diethyleneglycol, and the like.

When a rubbery polymer is desired, the grafting monomer can includeadiolefinic monomer such as butadiene, isoprene, 2, -3-dimethy1 butadiene, 2-chloro .butadiene, 2-cy-ano butadiene, 2-phenyl butadiene, 2-aceto'xy butadiene, or the like. The diolefinic monomer can bepresent-in amounts as low as about 5% of the grafting monomers, and-it is often desirable to employthe diolefinic hydrocarbons in amounts of from 60.to 100% of the grafting monomer.

Other grafting monomers which are suitably employed include the vinyl carboxylic esters, citraconamates, itaconamates, fumaramates, maleamates, citraconamides, itaconamides, fumaramides, maleamides, vinyl. pyridines, styrene and substituted styrenes, and the like. Minor amounts ofacrylonitrile or substituted acrylonitrile, acrylarnides,viny-l chloride,-vinylidene chloride, and the like can'also be used in the grafting monomer mixtures.

The vinyl carboxylic esters which are employed preferably are those of the formula CH2=oH-0-?[:Rl'

wherein R is an alkyl group containing from 1 to 9 7 carbon atoms. Typical esters which can be employed in practicing the invention include vinyl formate, vinylacetate, vinyl propionate, vinyl butyrate, vinyl 2-etl1yl hexanoate, and the like. The vinyl esters can form any part or all of the grafting monomer and are desirably employed inamountsof at least 50% by weight of the total weightof grafting monomers. As with allof the olefinic monomers .set out herein, one or more of the vinyl esters maybeemployed.

-A particularly-useful group of graftingrnonomers are the. methacrylatesof the formula wherein R isan alkyl group'of from-1' to8 carbon atoms. Typical methacrylates'which are suitably employed include methyl methacrylate, ethyl methacrylate, propyl rnethacrylate, nbutyl methacrylate, isobutyl methacrylate, hexyl methacrylate,-, octyl methacrylate, and 'the like. In the various esters described herein the alkyl groups can be either straight or branched-chain groups as desired.

The citraconamates which can be used are represented by the following formulas:

wherein R is either hydrogen or a methyl group, and R and R are as defined above. Typical acrylamides include acryiamide, N-methyl acrylamide, N-ethyl acrylamide, N-isopropyl acrylamide, N-n-zbutyl 'acrylamide, methacrylamide, N-methyl methacrylamide,.N-ethyl methacrylamide, N-isopropyl methacrylarnide, N,N-dimethy1 acrylamide, N,N-diethyl acrylamide, N,N-dimetl1yl methacrylamide, ethacrylamide, N-methyl ethacrylamide, apropyl acrylarnide, N-methyl-a-butyl acrylamide, etc.

As maleamides,wecanradvantageously use those represented by the following general formula:

wherein R and R6, are as abovedefined. Typical maleamides include maleamide, N-rnethyl maleamide, N-e-thyl maleamide, N-propyl maleamide, N-isopropyl maleamide, N-n-butyl maleamide, N,N' dimethyl maleamide, N,N'- diethyl maleamide, N,N-di-n-butyl maleamide, N-methyl- N-ethyl maleamide, N,N.'-tetramethyl maleamide, N,N'- vtetraethyl maleamide, N,N=dimethyl-N',N'-diethyl maleamide,-etc.

As,furnararrudes, we can advantageously use'those represented by the following general formula:

ll R 0 whereinR and R are as above defined. Typical fumaramides include furnaramide, -N -methy l fumaramide, N-

ethyl ifumaramide, 'N -propyl 'fumaramide, N-isopropyl fumaramide, 'N-n-butyl fumaramide, N,N-dirnethyl fumar am ide, N;N"di ethyl furnaramide,N,N'-di-n-butyl fumaramide, N-methyl-N'-ethyl fumaramide, N-methyl-N'- butyl fumaramide, N',N'-tetramethyl fumaramide, N,N'-

tetraethyl fumaramide, NQN-dimethyl-N',N-diethyl fumaramide, etc.

As itaconamides, we can advantageously use those represented by tile-following general formula:

wherein R and R are as above defined. Typical itaconamides include itaconarnide, N-methyl itaconamide, N-

ethyl itaconamide, N-n-butyl itaconarnide, N,N'-dimethyl itaconamide, N,N-diethyl itaconamide, the N,Nebutyl itaconami'des,. N,N-tetramethyl.itaconamide, etc.

As citraconamides, we can advantageously use those represented by the following general formula:

6 CH3OC-NR4 OH-(fi-lTI-Rr wherein R and R are as above defined. Typical citraconamides include citraconamide, N-methyl citraconamide, N-ethyl citraconamide, N-nbutyl citraconamide, N,N-dimethyl citraconamide, N,N'-diethyl citraconamide, the N,N-butyl citraconamides, N,N-tetramethyl citraconamide, etc.

The maleamates whose polymers we can advantageously use comprise those represented by the following general formula:

fiH-gO R5 CH(I'T-IIIR4 O R; wherein R R and R are as above defined. Typical maleamates include methyl maleamate, ethyl maleamate, propyl maleamate, n-butyl maleamate, N-methyl methyl maleamate, N-ethyl methyl maleamate, the N-butyl methyl maleamates, the N-methyl butyl maleamates, N- dimethyl methyl maleamate, N-dimethyl ethyl maleamate, N-dimethyl n-butyl maleamate, the N-dibutyl methyl maleamates, etc.

As fumaramates, we can advantageously use those represented by the following general formula:

wherein R R and R are as above defined. Typical fumaramates include methyl fumaramate, ethyl fumaramate, propyl fumaramate, n-butyl fumaramate, N-methyl methyl fumaramate, N-methyl ethyl fumaramate, the N- methyl butyl fumaramates, N-dimethyl methyl fumaramate, N-dimethyl ethyl fumaramate, N-dimethyl n-butyl fumaramate, the N-dibutyl methyl fumaramates, etc.

As itaconamates, we can advantageously use those represented by the following general formulas:

wherein R R and R are as above defined. Typical itaconamates include methyl it-aconamate, ethyl itaconamate, propyl itaconamate, the butyl itaconamates, N- methyl methyl itaconamate, N-methyl ethyl itaconamate, N-methyl propyl itaconamate, N-methyl n-butyl itaconamate, N-dimethyl methyl itaconamate, N-dimethyl ethyl itaconamate, N-dimethyl n-butyl itaconamate, the N-dibutyl methyl itaconamate, etc.

The styrene monomers which are suitable for use include styrene, a-methyl styrene, p-acetamino styrene, pmethyl styrene, a-acetoxy styrene, and the like.

The vinyl pyridines which are suitably employed include 2-vinyl pyridine, Z-vinyI-S-methyl pyridine, 2- methyl styrene, a-acetoxy styrene, and the like.

Other olefinic monomers containing an ethylenic or vinylic unsaturation are known in the art, and any of such polymerizable monomers are suitable for use in practicing the invention within the limits herein defined. The preparation of the graft polymers of this invention can be carried out either batchwise or in continuous fashion wherein the grafting monomer and a solution of the preformed polymer are continuously added to a reactor as in a continuous batch process or where product is also continuously withdrawn from a continuously circulating process.

In the polymers of this invention, the preformed acrylamidic polymer is present in an amount of from 20 to of the entire polymer, and preferably in an amount of from 20 to 60% of the total polymer. When the major portion of the grafting monomer is an acrylate, films having excellent vapor transmission characteristics are obtained with acrylamidic contents up to 60% of the total polymer. With other grafting monomers, the preformed acrylamidic polymer is desirably within the range of 20 to 40% of the total polymer for good vapor transmission characteristics. These polymers which have the characteristic of transmitting water vapor do not permit the passage of liquid water and hence are particularly useful for coating textile fabrics and leather to be used in the manufacture of waterproof clothing, footwear, and the like. The rubber-like polymers derived from the butadienes are especially valuable for this purpose. The polymers containing higher amounts of preformed acrylamidic polymer, as, for example, from 50 to 80% by weight, tend to swell in water and are permeable to the diffusion of salts and other water-soluble materials. These compositions are particularly useful as gelatin substitutes in photographic processes, with either black-and-white or color emulsions. They can also be used as sizing agents for textiles and papers, as thickening agents, as detergent additives, and the like. The polymers embodying the invention are particularly valuable as textile sizing agents because they show excellent adhesion to a wide variety of natural and synthetic fibers.

The invention is illustrated by the following examples of preferred embodiments thereof. These examples are included for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

Example 1 Twenty-five grams of polyacrylarnide is dissolved in 300 cc. of water and the following materials are added:

G. Methylacrylate 75.0 Divinylbenzene 0.5 Sodium dodecyl sulfate 0.8 Potassium persulfate 1.0 Sodium bisulfiite 0.5

Example 2 One hundred grams of polymethacrylamide is dissolved in 1000 cc. of Water and the following materials are added:

Butylacrylate 100.0 Ethylacrylate 100.0 Allylacrylate 1.0 Sodium octadecyl sulfate 2.0 Sodium persulfate 2.0 Sodium bisulfite 2.0

Themixture' is stirred at 5055 C.'for6 hours.- A smootl'h viseous'emulsion-is obtained. Five grams ofdimethylol'urea and 0.3 g; of diammo'nium phosphateare added as cross-linkingagent for the 'polymethacrylamide.- Cellulose acetate-'fabr-ic is *padde'd with the emulsion to give a'coating of 2.0-2.5 ounces peryard, ona dry'basis.

'Ihe'coated cloth-is dn'edat 110 C. The-coated fabric showsa Water vapor transmissionrat'e of 6070% of the untreated fabric. It holds a hydrostatic head of-6 feet of-water':

Example 3 Eighty grams of N- isopropylacrylamide and 20 g. of

. .acrylicacid are dissolved in 1200 cc. of water and 1.0 g.

of'potassiumpersulfate and 0.5 g. of dodecyl mercaptan are added; The solution is heated at- 50-60 C. for 24 hours to give a copolymer of the amide and acid. Sufiicientsodiumcarbonate is added to neutralize the carbo'xylf groups in the polymer and'produce a clear, viscous solution;

Thefollowingmaterials are added to the solution:

Ethyla'crylate 100.0 Vinyl acetate 20.0 Ammonium persulfate 1.6 sodium bislllfite' 1.0

Exan1ple'4 One hundred grains of poly N-methylmethacr-ylamide is dissolved in 2000 cc. of water and the following "materials are added:

Isobutylacrylate 325.0 N methylmethacrylaniide 75.0 Sulfonated mineral oil; 3.0- Ammoniurn persulfate 5.0 Sodium persulfate 3.0

The miXtureis stiiredat 50-55" C. for 6 'hours'J A smooth; sfa'ble emulsion is'obtained. l Fivegrams of ureaformaldehyde prepolymer and 0.5 g. of diammom'um phosphate are added and the emulsion is coated on nylon sharkskin fabrieto give a dry-weight deposit of 3.5 ouhces per square yard. The fabric is dried at 1 10 C. The coated fabric has a water vapor transmission rate that is 70-7 5%'of the uncoatedfabric. The coated-fabric will hold a hydrostatic head of 6 feet of water.

EkamplS A 'copolymer is made having the compositionz' 70% N methylacryla'mide30% N butylacrylamide. One hundred grams of the copolymer is dispersedin 2500 cc. of wat'er and the following materials' are added.

G.- Z-ethyIlieXylacryIate e v e r -e- 1 120.0 Methoxyethyl methacrylate 80.0 1 Sodium salt of dodecyl benzene 2.0 Ammonium persulfate n 2.5

The mi'xturdis' stirred-at 60" C. for 4 -hours'. This composition is usefulforcoating cloth and leather.

Example 6 A'copolymer is made havingthe composition: 65%

. N'- ethylacrylamide35% N,N dimethyl acr'ylamid'e.

One hundred parts of the polymer-is dissolved' in"400 parts of 8-methoxyetha-nol.--' Seventy-five parts of methylacrylate-and 1.0par-tofbenzoy-l-peroX-ide are i added. The solutionisheated at 6070' C. for'20 hours. A

12 clear, viscous solution is obtained.- Films were coated on glass plates andthe solvent was' evaporated at 90- 100 C. A clear film was produced. This film is per meable to ions and can be'used as a gelatin substitute.

Example'7 Ten g. polyacrylam'idewas dissolved in 100 cc. of water and the following materials were added.

G; Vinylacetate 10.0 Potassium persulfate 0.1 Sodium dodecyl suifate 0.2

The mixtur'e was stirred at C. for 12- hours to produee a stable emulsion of polyvinyl acetate. The-emulsion was coated on glass plates and th'e water 7 was "evaporated at 70-80 CLto'give a'clear film that showed very strong adhesion to the glass. This product is useful 'as a gelatin substitute in photography.

Example '8 Ten g. polymethacrylamide was dissolved in 100 cc. of Water and the following materials were added.

G. Methyl metha'cryl'ate' 25.0 Ammonium persulfate 0.2 Sodium 'octadec'yl sulfate 0.4

Themixture was-stirred-at C. for -8 hours. A stable emulsion was obtained; Evaporation of the-water produced a clear filmthat showed'only a limited-swelling when imersed in water. This material is useful as a sizing agent forpaper; It is alsouseful'as-agelatin-substitute because it is permeable to salt solutions.

Example 9 Ten g. of N-methyl methacrylamide Was dissolved in cc. of water along with 0.1 g. sodium persulfate and 0.1 g. sodium bisulfite. The solution was stirred at 30 35 C. for 8 hours to produce a solution of poly N-methyl metha'crylamidei The following material's were added to the solution? 2 G. Butylm ethacrylate 10Z0 Ootylm'ethacrylate "an.-- 10.0 Sulfonated-miiiral 'oil2Aeemsnsuasfiemeen- 0.4

Divinyl benzene- I h 0.1 Sodium ersulfate;snemssrfinesnnmta- 0.3

The mixture wa's'stirred at 60 C. for 6'hours. A smooth, uniform emulsion was obtained. In order to improve the resistance of the film to water, 0.5 g. trimethylol melamine and 0.1 g.. diarnmonium hydrogen phosphate were added to the emulsion: Cellulose acetate cloth was coated with the emulsion togive a dry weight application of 2.0 ounces per square yard. The cloth was then dried at C. The coated clothshowed a high transmission rate for water vapor but was impermeable to liquid water. The emulsion can also be used for the treatment of leather.

Vinyl acetate: 25.0 Diethyl fumarat 25.0 Potassium persulfatem 0.4 Sodium.octadecyl"sulfate; 1.0

The mixture was stir-red--at-60"- C- -fer-10 hours. The emulsion was coated-on paper anddried-at'110" C. A smooth, hardglaze was produced on the paper surface.

Example-11 A copolyme'r' was preparedfro'm l'part 'acrylamide' 13 and 2 parts N,N-dimethyl acrylamide. One hundred g. of the copolymer was dissolved in 400 cc. of water and the following materials were added.

Styrene 20.0 Sulfonated olive oil 0.3 Ammonium persulfate 0.2 The mixture was stirred at 65 C. for 3 hours. This product is useful as a sizing agent for textile fibers.

Example 12 Ten g. of N-ethyl methaerylamide polymer was dissolved in 100 cc. of water and the following materials were added.

G. n-Butyl vinyl ether 5.0 Acrylic acid 5.0 Potassium persulf 0.1

Sulfonated mineral oil 0.2

The mixture was stirred at 60 C. for 8 hours. The acid groups in the polymer were neutralized by adding sodium carbonate. The product is valuable as a textile sizing agent. It shows good adhesion to synthetic fibers such as polyamides, polyacrylonitrile, polyesters, etc.

Example 13 A copolymer was made having the composition 1 part N-ethyl acrylamide-l-l part acrylamide. Ten g. of the copolymer was dissolved in 150 g. of water and the following materials were added.

G. Vinyl Z-ethyl hexanoate 25.0 Dibutyl mal 5.0 Sodium dodecyl sulfate 0.8 Potassium persulfa 0.4

The mixture was stirred at 60 C. for 20 hours. An emulsion was obtained. This product is useful for coating fabrics and leather, as described in Example 9. The coated materials will transmit water vapor but will not allow the passage of liquid water.

Example 14 Ten g. of n-butyl methacrylamide and 0.1 g. benzoyl peroxide were dissolved in 100 cc. of ethyl alcohol. The solution was heated at 60 C. for 20 hours. A viscous solution of poly-n-butyl methacrylamide was produced. Ten g. of butyl methaerylate and 0.1 g. benzoyl peroxide were added to the solution and the mixture was heated at 60 C. for 24 hon-rs. Films coated from the solution were clear and tough. They had a high transmission rate for water vapor but were impermeable to liquid Water.

Example 15 Ten g. of poly N-isopropylacrylamide was dissolved in 100 cc. of water and the following materials were added.

G. Butadiene 7.0 Styrene 3.0 Sodium dodecyl sulf 1.0 Potassium persulfat 0.1 Sodium bisulfi 0.1

the capacity to breathe whereby the discomfort attendant to most waterproof fabrics is largely overcome. By a suitable choice of composition, a class of polymeric materials which can serve as gelatin substitutes, additives or extenders in photographic processes is provided. Such materials are compatible with gelatin and can serve in any of the applications wherein gelatin is ordinarily employed including use in the photographic emulsions carrying light-sensitive materials such as the silver halides,

By the use of suitable cross-linking or hardening agents for the acrylamidic preformed polymer, the water insolubility of the final product is enhanced. Similarly, divinyl cross-linking agents can be employed for imparting solvent resistance to the final polymer by cross-linking the portion of the graft copolymer built up during the grafting step.

The invention thus offers a solution to problems which have faced the workers in the polymeric arts for many years. The utility of the polymers is greatly extended, and it is possible by a suitable choice of ingredients to prepare products having closely controlled properties within desired ranges of physical and chemical characteristics.

Although the invention has been dmcribed in detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

This application is a continuation of Serial No. 444,648, filed July 20, 1954 (now abandoned).

We claim:

1. Polymeric material capable of freely transmitting water vapor while preventing the passage of liquid water and being the graft copolymer of a mixture of 1) a homopolymer of a monomer of the formula:

wherein R' and R" are selected from the group consisting of hydrogen and alkyl groups of 1 to 4 carbon atoms, (2) a monomeric alkyl acrylate wherein the alkyl group contains 1 to 8 carbon atoms and (3) a cross-linking agent selected from the group consisting of divinyl benzene, a-llyl acrylate and diallyl phthalate, said homopolymer and said acrylate being present in said graft copolymer in the Weight ratio of 20 to 60% of the said homopolymer to to 40% of the said acrylate, and said cross-linking agent being present in said graft copolymer in an amount of 0.5 to 15% based on the weight of the said homopolymer.

2. The polymeric material according to claim 1 wherein the said homopolymer is polyacrylamide, wherein the said acrylate is methyl acrylate and wherein the said cross-linking agent is divinyl benzene.

3. Polymeric material capable of freely transmitting water vapor while preventing the passage of liquid water and being the graft copolymer of mixture of 25 parts by weight of polyacrylamide, 75 parts by weight of methyl acrylate and 0.5 part by weight of divinyl benzene.

4. A procms for preparing polymeric material capable of freely transmitting water vapor while preventing the passage of liquid Water which comprises heating at 30 to C. an aqueous mixture comprising (1) a homopolymer of a monomer of the formula:

W CHFCH-P3N/ wherein R and R" are selected from the group consisting of hydrogen and alkyl groups of 1 to 4 carbon atoms, (2) a monomeric alkyl acrylate wherein the alkyl group contains 1 to 8 carbon atoms, (3) a cross-linking agent selected fl oni the gr oup consisting of divinyl benzene, allyl acrylate and diallyl phthalate-and (-4) aperoxide polymerization catalyst, Qsaid homopolymer and said acrylate being present in said mixture in the weight'ratio of to of the saidhomopolymer to to-40% of the said acrylate, and said cross-linkingagentbeing present, in said mixture in an amountof 0.5 to 15% based on the weight of the said homopolymer.

5. The process according to claim 4 wherein the said homopolymer is polyacrylalm'de, wherein the -said acrylate is methyl acrylate and wherein the said crosslinking agent is divinyl benzene.

6. A process for preparing -po1ymeriema-terial capable of freely transmitting water vapor while preventing the passage'of liquid'waterwhich comprises heating at 30 to C. an aqueous mixture'comprising 25 parts by weightof polyaeryla nide, 75 parts by weight of methyl a'crylate and 05 part by :weight of di vinylv benzene, in the presence of -a peroxide polymerization catalyst.

References Cited in i'n e file of this patent UNITED STATES PATENTS OTHER REFERENCES Whitby: Synthetic Rubber, pages 16-17, published by; Wiley, New York (1954). 

1. POLYMERIC MATERIAL CAPABLE OF FREELY TRANSMITTING WATER VAPOR WHILE PREVENTING THE PASSAGE OF LIQUID WATER AND BEING THE GRAFT COPOLYMER OF A MIXTURE OF (1) A HOMOPOLYMER OF A MONOMER OF THE FORMULA: 